smb3: Fix out-of-bounds bug in SMB2_negotiate()

While addressing some warnings generated by -Warray-bounds, I found this
bug that was introduced back in 2017:

  CC [M]  fs/cifs/smb2pdu.o
fs/cifs/smb2pdu.c: In function ‘SMB2_negotiate’:
fs/cifs/smb2pdu.c:822:16: warning: array subscript 1 is above array bounds
of ‘__le16[1]’ {aka ‘short unsigned int[1]’} [-Warray-bounds]
  822 |   req->Dialects[1] = cpu_to_le16(SMB30_PROT_ID);
      |   ~~~~~~~~~~~~~^~~
fs/cifs/smb2pdu.c:823:16: warning: array subscript 2 is above array bounds
of ‘__le16[1]’ {aka ‘short unsigned int[1]’} [-Warray-bounds]
  823 |   req->Dialects[2] = cpu_to_le16(SMB302_PROT_ID);
      |   ~~~~~~~~~~~~~^~~
fs/cifs/smb2pdu.c:824:16: warning: array subscript 3 is above array bounds
of ‘__le16[1]’ {aka ‘short unsigned int[1]’} [-Warray-bounds]
  824 |   req->Dialects[3] = cpu_to_le16(SMB311_PROT_ID);
      |   ~~~~~~~~~~~~~^~~
fs/cifs/smb2pdu.c:816:16: warning: array subscript 1 is above array bounds
of ‘__le16[1]’ {aka ‘short unsigned int[1]’} [-Warray-bounds]
  816 |   req->Dialects[1] = cpu_to_le16(SMB302_PROT_ID);
      |   ~~~~~~~~~~~~~^~~

At the time, the size of array _Dialects_ was changed from 1 to 3 in struct
validate_negotiate_info_req, and then in 2019 it was changed from 3 to 4,
but those changes were never made in struct smb2_negotiate_req, which has
led to a 3 and a half years old out-of-bounds bug in function
SMB2_negotiate() (fs/cifs/smb2pdu.c).

Fix this by increasing the size of array _Dialects_ in struct
smb2_negotiate_req to 4.

Fixes: 9764c02fcbad ("SMB3: Add support for multidialect negotiate (SMB2.1 and later)")
Fixes: d5c7076b772a ("smb3: add smb3.1.1 to default dialect list")
Cc: stable@vger.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/cifs/smb2pdu.h b/fs/cifs/smb2pdu.h
index d85edf5..a5a9e33 100644 (file)
--- a/fs/cifs/smb2pdu.h
+++ b/fs/cifs/smb2pdu.h
@@ -286,7 +286,7 @@ struct smb2_negotiate_req {
        __le32 NegotiateContextOffset; /* SMB3.1.1 only. MBZ earlier */
        __le16 NegotiateContextCount;  /* SMB3.1.1 only. MBZ earlier */
        __le16 Reserved2;
-       __le16 Dialects[1]; /* One dialect (vers=) at a time for now */
+       __le16 Dialects[4]; /* BB expand this if autonegotiate > 4 dialects */
 } __packed;
 
 /* Dialects */